Examples of prior art in securing coverings to roof structures include U.S. patents:
4,885,887 PA1 4,932,171 PA1 3,900,102 PA1 1,174,024 PA1 871,960
and Canadian patents:
While differing in several respects from each other, the structure and methods disclosed in these patents require extensive time and labor to install.
A further consideration is the extent to which a roof perimeter fastening system can withstand the forces imposed by winds passing over the roof and, in particular, the shear forces imposed at angles to the perimeter fastening means. For example, it is common practice to secure the perimeter securement elements to the roof structure with a plurality of spaced screw fasteners driven through respective plates or washers. An example is shown in the above mentioned U.S. Pat. No. 4,932,171 wherein a plurality of spaced screws 23 or 32 is utilized. Clearly, force-resistant stresses are concentrated at the spaced fasteners.
In practice, a perimeter securement membrane is positioned on the underlying roof insulation. The plurality of plates or washers are then manually placed on the perimeter membrane at intervals therealong. While the specifications may require that the plates be carefully positioned at a predetermined distance from the wall and at equal distances from each other, the pressures of time or the inexperience of the installers may result in a haphazard pattern not in conformance with the specifications.